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Caspian seal

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Caspian seal
A Caspian seal in Iran
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Phocidae
Genus: Pusa
Species:
P. caspica
Binomial name
Pusa caspica
(Gmelin,1788)
Caspian seal range
Synonyms
Phoca caspica

TheCaspian seal(Pusa caspica,syn.Phoca caspica)[1]is one of the smallest members of theearless sealfamily and unique in that it is found exclusively in the brackishCaspian Sea.It lives along the shorelines, but also on the many rocky islands and floating blocks of ice that dot the Caspian Sea. In winter and cooler parts of the spring and autumn season, it populates the northern Caspian coastline. As the ice melts in the summer and warmer parts of the spring and autumn season, it also occurs in the deltas of theVolgaandUral Rivers,as well as the southern latitudes of the Caspian where the water is cooler due to greater depth.

Evidence suggests that the colonization events of Caspian seals were probably facilitated by river connections from the Arctic that have since disappeared, landlocking the populations sometime before the majorPleistoceneglaciations.[2]

Description[edit]

Adults are about 126–129 cm (50–51 in) in length. Males are longer than females at an early age, but females experience more rapid growth until they reach ten years of age. Males can grow gradually until they reach an age of about 30 or 40 years.[3]Adults weigh around 86 kg (190 lb); males are generally larger and bulkier. Theirdental formulais3.1.4.22.1.4.1.[4]

The skull structure of the Caspian seal suggests it is closely related to theBaikal seal.In addition, the morphological structures in both species suggest they are descended from theringed sealwhich migrated from larger bodies of water around two million years ago.[5]

Caspian seals can be found not only along the shorelines, but also on the many rocky islands and floating blocks of ice that dot the Caspian Sea. As the ice melts in the warmer season, they can be found on the mouths of the Volga and Ural Rivers, as well as the southern latitudes of the Caspian where cooler waters can be found due to greater depth.[citation needed]

One notable attribute of Caspian seals is its adaptation to a wide range of air temperatures and given the extreme climate of its habitat. Temperatures in the Caspian Sea range from -35 °C in the winter months to +40 °C in the summer, sitting at the southernmost limit for ice formation in winter with sub-tropical conditions for the rest of the year.[2]In winter, and cooler parts of the spring and autumn season, the seals populate the Northern Caspian. In the first days of April, spring migration to the southern part of the Caspian Sea begins with mature female seals and their pups, during this migration hungry seals eat the fish in the nets. Male mature seals stay in the northern Caspian Sea longer and wait until the moulting is completed. In summer, seals find empty places in the western part of Apsheron for resting. In the eastern part, the most crowded place used to be theOgurchinskiy Island,but by 2001, fewer than 10 pups were recorded on Ogurchinsky, some of which were killed by people on the island.[citation needed]

Diet[edit]

Caspian seals are primarilypiscivorous.They eat a variety of food depending on season and availability. A typical diet for Caspian seals found in the northern Caspian sea consists of crustaceans and various fish species, such asClupeonella engrauliformis,C. grimmi,C. caspia,Gobiidae,Rutilus caspicus,Atherina boyeri,andSander lucioperca.Caspian seal adults eat about 2–3 kg (4–7 lb) of fish a day and almost a metric ton of fish per year.[6]

In autumn and winter, Caspian seals prey mostly onsculpins,gobies,and crustaceans while inhabiting shallow waters in the northern part of the sea. During the summer, in the southern part of the Caspian Sea, they eatherring,roach,carp,sprat, and smelt. When Caspian seals live in estuaries, they eat large amounts of the freshwater species,Sander lucioperca.Other prey include shrimp, crab, and silversides.[7]

Being one of the top predators in the ecosystem, Caspian seals had hazardous chemicals found inside their bodies such asheavy metals,organochlorine compounds,andradionuclides.[8]

Behavior and ecology[edit]

Caspian seals are shallow divers, typically diving 50 m (160 ft) for about one minute, although scientists have recorded Caspian seals diving deeper and for longer periods of time. After foraging during a dive, they rest at the surface of the water.[9]

In the summer and winter, during mating season, Caspian seals tend to live in large groups. At other times of the year, these seals are solitary. During the summer, however, they make aggressive snorts or use flipper waving to tell other seals to keep their distance. Little else is known about their behavior.[9]

Reproduction[edit]

Male and female Caspian seals are monogamous. Among breeding seals, a lack of fighting for a mate seems prevalent. In late autumn, Caspian seals travel to the northern part of the Caspian Sea where the water is shallow and frozen to give birth in secluded areas on ice sheets after a gestation period of 11 months. Normally, pregnancy rates are 40 to 70%, but are currently at an all-time low of 30%. In late January to early February, female seals give birth to one pup each. Similar to other ringed seals, these pups are born with whitepelagesand weigh about 5 kg (11 lb). Caspian seals employ acapital breedinglactation strategy, where the mother will fast while nursing the pup, sometimes with a small amount of supplemental feeding. Pups are weaned after a few weeks.[10]The pups' white coats aremoltedat around three weeks to a month. Male pups become sexually mature after six to seven years, whereas female pups sexually mature after five to seven years. Newborn pups are not fully grown until 8 to 10 years after they are born.[11]Breeding begins a few weeks after the birth of last year's pup around late February to mid March. Breeding usually occurs after weaning of a newborn pup, but can begin while the pup is still nursing. Caspian seals migrate back to the southern part of the Caspian Sea after the breeding season and molting in late April because the north begins to warm with constant ice melting. The southern region of the Caspian Sea has deep, colder waters where the seals spend the summer months.[12]

Diseases[edit]

Several recent cases of large numbers of Caspian seals dying due tocanine distempervirus have been reported, in 1997, 2000 and 2001.[3]In April 2000, a mass die-off of Caspian seals was first reported near the mouth of theUral Riverin Kazakhstan. It spread south to theMangistauregion, and by the end of May, more than 10,000 seals had died along the Kazakhstan coast. High death rates were also recorded in May and June along theApsheron peninsulaof Azerbaijan and the Turkmenistan coast.[13]

Clinical signs of infected seals included debilitation, muscle spasms, ocular and nasal exudation, and sneezing. Necropsies performed in June 2000 on eight Azerbaijan seals revealed microscopic lesions, including bronchointerstitialpneumonia,encephalitis,pancreatitisand lymphocytic depletion in lymphoid tissues. Similar lesions were also discovered on four seals from Kazakhstan.Morbillivirusantigen was also detected in multiple tissues, including lung,lymph nodes,spleen, brain, pancreas, liver, andepithelial tissueof the reproductive, urinary, and gastrointestinal tracts. Such tissue lesions are characteristic of distemper in both terrestrial and aquatic mammals.[13]

Tissues from 12 carcasses found inKazakhstan,Azerbaijan,andTurkmenistanwere examined formorbillivirusnucleic acid. Sequences from the examination showed that canine distemper virus, which is part of the genusMorbillivirus,was the primary cause of death. The sequences also proved that seals from widely separated regions of the Caspian Sea were infected by the same virus. This finding established spatial and temporal links between the seal deaths in these regions. The sequences were also identical to that of canine distemper virus found in the brain tissue of a seal that died in 1997 and showed no morbillivirus lesions. This suggests persistence of canine distemper virus in the Caspian seal population over a span of several years or repeated spillover from the same terrestrial reservoir.[13]

Another study in 2000 using 18 Caspian seal corpses found several concurrent bacterial infections that could have contributed to the illness of the affected seals. These includeBordetella bronchiseptica,Streptococcus phocae,Salmonella dublin,andS. choleraesuis.Corynebacterium caspium,a new bacterium, was identified in one of the seals, and poxvirus,Atopobacter phocae,Eimeria- andSarcocystis-like organisms, and aHalarachnespecies were identified in Caspian seals for the first time. The study also asserts that the “unusually mild” winter that preceded the die-off in 2000 could have contributed to its cause “through increased ambient air pressure and accelerated disappearance of ice cover at the breeding areas in the northern Caspian Sea.”[14]

Threats[edit]

A century ago, their population was estimated at 1.5 million seals; in 2005, 104,000 remained, with an ongoing decline of 3–4% per year, primarily due to human influence (i.e. fisheries bycatch and habitat encroachment), outbreaks of Phocidae Distemper Virus (PDV), climate change, and pollution.[15][16]By 2022, theCaspian Environmental Protection Centerestimated the population at 70,000.[17]

In a three-week period in February 1978,wolveswere responsible for the killing of numerous seals nearAstrakhan.An estimated 17 to 40% of the seals in the area were killed, but not eaten.[18]

Due to increased industrial production in the area, pollution has had an effect on the survival of the Caspian seal. From 1998 to 2000, the concentration of zinc and iron increased dramatically in the tissue of dead, diseased seals. This suggests these elements are causative agents in compromising the Caspian seal's immune system.[19]

Sea eaglesare known to hunt these seals, which results in a high number of fatalities for the juveniles. They are also hunted by humans for subsistence and commerce. As of 2006,commercial icebreaker routes have passed through areas with high Caspian seal pup concentrations, which may contribute to loss of habitat.[20]

For threats related to migration, high density seal aggregations were recorded in November 2009 and 2010 CISS helicopter surveys inKenderli Bay,but the integrity of seal habitat in Kenderli Bay is currently threatened by an imminent large-scale coastal resort development. This resort development can be a serious disturbance for seals. The local authorities have been advised about the need to preserve the seal habitats in the bay, but it is not yet clear what steps are planned to achieve this. According to the present studies, Kenderli Spit plays an important role for the seasonal migration of the Caspian seals and is recommended to be a protection area.

In December 2022, asubstantial die-offwas reported, with initial reports of 700 corpses later revised upwards to 2,500. The cause is unknown.[17]

See also[edit]

References[edit]

  1. ^abGoodman, S.; Dmitrieva, L. (2016)."Pusa caspica".IUCN Red List of Threatened Species.2016:e.T41669A45230700.doi:10.2305/IUCN.UK.2016-1.RLTS.T41669A45230700.en.Retrieved19 November2021.
  2. ^abPALO, JUKKA U.; VÄINÖLÄ, RISTO (2006-04-27)."The Enigma of the landlocked Baikal and Caspian seals addressed through phylogeny of phocine mitochondrial sequences".Biological Journal of the Linnean Society.88(1): 61–72.doi:10.1111/j.1095-8312.2006.00607.x.ISSN0024-4066.
  3. ^abWilson, Susan; Eybatov, Tariel; Amano, Masao; Jepson, Paul; Goodman, Simon (2014)."The Role of Canine Distemper Virus and Persistent Organic Pollutants in Mortality Patterns of Caspian Seals (Pusa caspica) ".PLOS ONE.9(7): e99265.Bibcode:2014PLoSO...999265W.doi:10.1371/journal.pone.0099265.PMC4079250.PMID24987857.
  4. ^T.A. Jefferson; S. Leatherwood; M.A. Webber."Marine Mammals of the World: Caspian seal (Phoca caspica)".species-identification.org.Retrieved7 December2022.
  5. ^Endo, H.; Sakata, S.; Arai, T.; Miyazaki, N. (2001). "The Muscles of Mastication in the Caspian Seal (Phoca caspica) ".Anatomia, Histologia, Embryologia.31(5): 262–265.doi:10.1046/j.1439-0264.2002.00372.x.PMID12484416.S2CID30684638.
  6. ^Khuraskin, L.; Pochotoyeva, N. (1997). "Status of the Caspian Seal Population".Caspian Environment Program:86–94.
  7. ^Grimeks, B. (1990).Grimeks Encyclopedia of Mammals(Second ed.). New Jersey: McGraw-Hill. pp. 220–238.
  8. ^Ikemoto, T.; Kunito, T.; Watanabe, I.; Yasunaga, G.; Baba, N.; Miyazaki, N.; Petrov, E. A.; Tanabe, S. (2004). "Comparison of trace element accumulation in Baikal seals (Pusa sibirica), Caspian seals (Pusa caspica) and northern fur seals (Callorhinus ursinus) ".Environmental Pollution.127(1): 83–97.Bibcode:2004EPoll.127...83I.doi:10.1016/s0269-7491(03)00251-3.PMID14553998.
  9. ^abReeves, R; Stewart, B; Clapham, P; Powell, J (2002).Guide to Marine Mammals of the World.New York: Chanticlear Press.
  10. ^Wilson, Susan C.; Dolgova, Evgeniya; Trukhanova, Irina; Dmitrieva, Lilia; Crawford, Imogen; Baimukanov, Mirgaliy; Goodman, Simon J. (2016-11-15)."Breeding behavior and pup development of the Caspian seal,Pusa caspica".Journal of Mammalogy:gyw176.doi:10.1093/jmammal/gyw176.ISSN0022-2372.
  11. ^Easley-Appleyard, B. (2006)."Pusa Caspica Caspian Seal".Animal Diversity Web.Retrieved23 October2014.
  12. ^Hogan, Michael C., ed. (2010)."Caspian Seal".The Encyclopedia of Earth.Retrieved24 October2014.
  13. ^abcKennedy, Seamus; Kuiken, Thijs; Jepson, Paul; Deaville, Robert; Forsyth, Morag; Barrett, Tom; van de Bilt, Marco; Osterhaus, Albert; Eybatov, Tariel; Callan, Duck; Kydyrmanov, Aidyn; Mitrofanov, Igor; Wilson, Susan (2000)."Mass die-off of Caspian Seals by Canine Distemper Virus".Emerging Infectious Diseases.6(6): 637–639.doi:10.3201/eid0606.000613.PMC2640919.PMID11076723.
  14. ^Kuiken, T.; Kennedy, S.; Barrett, T.; Van de Bilt, M.W.G.; Borgsteede, F.H.; Brew, S.D.; Codd, G.A.; Duck, C.; Deaville, R.; Eybatov, T.; Forsyth, M.A.; Foster, G.; Jepson, P.D.; Kydyrmanov, A.; Mitrofanov, I.; Ward, C.J.; Wilson, S.; Osterhaus, A.D.M.E. (2006)."The 2000 Canine Distemper epidemic in Caspian Seals (Phoca caspica): Pathology and analysis of contributory factors ".Veterinary Pathology.43(3): 321–338.doi:10.1354/vp.43-3-321.PMID16672579.
  15. ^Kajiwara, Natsuko; Watanabe, Mafumi; Wilson, Susan; Eybatov, Tariel; Mitrofanov, Igor V.; Aubrey, David G.; Khuraskin, Lev S.; Miyazaki, Nobuyuki; Tanabe, Shinsuke (March 2008)."Persistent organic pollutants (POPs) in Caspian seals of unusual mortality event during 2000 and 2001".Environmental Pollution.152(2): 431–442.Bibcode:2008EPoll.152..431K.doi:10.1016/j.envpol.2007.06.075.ISSN0269-7491.PMID17900768.
  16. ^Dmitrieva, Lilia; Kondakov, Andrey; Oleynikov, Eugeny; Kydyrmanov, Aidyn; Karamendin, Kobey; Kasimbekov, Yesbol; Baimunkanov, Mirgaliy; Wilson, Susan; Goodman, Simon (2013)."Assessment of Caspian Seal By-Catch in an Illegal Fishery Using an Interview-Based Approach".PLOS ONE.8(6): e67074.Bibcode:2013PLoSO...867074D.doi:10.1371/journal.pone.0067074.PMC3694144.PMID23840590.
  17. ^ab"Russia: Bodies of 2,500 seals found along Caspian Sea coast".BBC.4 December 2022.Retrieved4 December2022.
  18. ^Rumyantsev, V. D.; Khuraskin, L. S. (1978). "New data on the mortality of the Caspian seal due to wolves". In Panteleev, P. A.; et al. (eds.).Page 187 in Congress of the All-Union Theriological Society.Vol. ZR 116 (Second ed.). Moscow: Nauka. p. 5669.
  19. ^Anan, Y.; Kunito, T.; Ikemoto, T.; Kubota, R.; Watanabe, I.; Tanabe, S.; Miyazaki, N.; Petrov, E.A. (2002). "Elevated concentrations of trace elements in Caspian Seals (Phoca caspica) found stranded during the mass mortality events in 2000 ".Archives of Environmental Contamination and Toxicology.42(3): 354–362.Bibcode:2002ArECT..42..354A.doi:10.1007/s00244-001-0004-7.PMID11910465.S2CID24430326.
  20. ^Harkonen, Tero; Jüssi, Mart; Baimukanov, Mirgaly; Bignert, Anders; Dmitrieva, Lilia; Kasimbekov, Yesbol; Verevkin, Mikhail; Wilson, Susan; Goodman, Simon J. (Jul 2008). "Pup Production and Breeding Distribution of the Caspian Seal (Phoca caspica) in Relation to Human Impacts ".Ambio: A Journal of the Human Environment.37(5): 356–361.Bibcode:2008Ambio..37..356H.doi:10.1579/07-r-345.1.PMID18828281.S2CID21482406.

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